Change in transit use maps

These maps were derived by calculating the percentage of workers
16 and over who reported that they taken public transit to work in
2000 and dividing this number by the percentage of workers 16 and
over who reported they had taken public transit to work in 1990.
The result (numbers running from 0 to 16) was expressed as a
percentage of change (.5 = loss of 50%; 1 = no change; etc.).
Because percentages were involved in the first calculation, the
change from one decade to the next should not have been affected by
a change in population, but it should be remembered that [1]
transit data come from the Census Bureau's sample survey (part 3A,
the long form) and are not as reliable as the 100% data; and [2] in
parts of the suburbs only a very small percentage of workers took
public transit to work. As a result, the suburban data tend to be
volatile. An increase from 1% to 2% would count on these maps as a
100% gain; a perhaps more significant increase in an urban tract
from 40% to 50% would be treated as a gain of 25%.

Tracts with fewer than 50 people or those for which no
mode-of-transit-to-work figures were reported for either 1990 or
2000 are omitted from this analysis.